[PATCH v4 09/21] refs: add method to rename refs

@@ -1133,6 +1133,11 @@ int delete_refs(struct string_list *refnames)
 	return the_refs_backend->delete_refs(refnames);
 }
 
+int rename_ref(const char *oldref, const char *newref, const char *logmsg)
+{
+	return the_refs_backend->rename_ref(oldref, newref, logmsg);
+}
+
 const char *resolve_ref_unsafe(const char *ref, int resolve_flags,
 			       unsigned char *sha1, int *flags)
 {

@@ -2502,7 +2502,8 @@ static int commit_ref_update(struct ref_lock *lock,
 			     const unsigned char *sha1, const char *logmsg,
 			     int flags, struct strbuf *err);
 
-int rename_ref(const char *oldrefname, const char *newrefname, const char *logmsg)
+static int files_rename_ref(const char *oldrefname, const char *newrefname,
+			    const char *logmsg)
 {
 	unsigned char sha1[20], orig_sha1[20];
 	int flag = 0, logmoved = 0;

@@ -3592,6 +3593,7 @@ struct ref_storage_be refs_be_files = {
 	files_peel_ref,
 	files_create_symref,
 	files_delete_refs,
+	files_rename_ref,
 
 	files_resolve_ref_unsafe,
 	files_verify_refname_available,

@@ -67,6 +67,13 @@ int do_for_each_per_worktree_ref(const char *submodule, const char *base,
 				 each_ref_fn fn, int trim, int flags,
 				 void *cb_data);
 
+/*
+ * Check if the new name does not conflict with any existing refs
+ * (other than possibly the old ref).  Return 0 if the ref can be
+ * renamed to the new name.
+ */
+int rename_ref_available(const char *oldname, const char *newname);
+
 enum peel_status {
 	/* object was peeled successfully: */
 	PEEL_PEELED = 0,

@@ -246,6 +253,7 @@ typedef const char *resolve_ref_unsafe_fn(const char *ref,
 typedef int verify_refname_available_fn(const char *refname, struct string_list *extra, struct string_list *skip, struct strbuf *err);
 typedef int resolve_gitlink_ref_fn(const char *path, const char *refname,
 				   unsigned char *sha1);
+typedef int rename_ref_fn(const char *oldref, const char *newref, const char *logmsg);
 
 /* iteration methods */
 typedef int head_ref_fn(each_ref_fn fn, void *cb_data);

@@ -284,6 +292,7 @@ struct ref_storage_be {
 	peel_ref_fn *peel_ref;
 	create_symref_fn *create_symref;
 	delete_refs_fn *delete_refs;
+	rename_ref_fn *rename_ref;
 
 	resolve_ref_unsafe_fn *resolve_ref_unsafe;
 	verify_refname_available_fn *verify_refname_available;